Protected offshore storage facility

ABSTRACT

In combination, a diked area in a body of water, a floating tank moored in the diked area for storing liquid of less density than the density of water, and a fixed roof on the tank.

United States [Patent 1191 Bliss, Jr. [45] Oct. 29,1974

[54] PROTECTED OFFSHORE STORAGE 3,155,280 11/1964 FACILITY 3,167,203 l/ 1965 3,289,417 12/1966 [7 51 Inventor: Woodrow E. Bllss, Jr., Plttsburgh, 5,793 4 1969 Pa. 3,708,982 1/1973 [73] Assignee: Pittsburgh-Des Moines Steel 213;; Company, Pittsburgh, Pa. 3:779: 93 12 973 [22] Filed: Apr. 26, 1973 Primary ExaminerW. C. Reynolds [211 Assistant Examiner-Philip C. Kannan Attorney, Agent, or Firm-Shoemaker and Mattare [52] US. Cl. 61/1, 61/46, 114/.5 T [51] Int. Cl E02b 3/00, E02b 3/04 57 TRA T [58] Field of Search 61/1, 1 F, 63, 46, 46.5;

114/5 T 74 T In comblnatlon, a dll ed area 1n a body of w ater, a

fioatmg tank moored 1n the d1ked area for stonng Im- [56] References Cited ?ixd 59f lefs s deirkllsity tEan-the density of water, and a UNITED STATES PATENTS e e 2,945,465 7/1960 Barton 61/1 R x 10 Claims 15 Dmwmg gums PROTECTED OFFSHORE STORAGE FACILITY BACKGROUND OF THE INVENTION I This invention relates to storage facilities for the stor age of liquid products such as crude oil and the like, andin particular, relates to such storage facilities which are situated offshore in a body of water, such as a bay or ocean or the like.

In recent years the supply of energy sources has become critically short and many countries must rely increasingly on imported energy materials, such as crude oil and the like. Such imported crude oils are typically stored in tank farms or large storage facilities comprising a plurality of large storage tanks untilsuch time as the crude oil is taken from the tanks and refined or otherwise processed or used as needed. Most tank farms 'many instances, either physically or economically impractical.

Accordingly, it has been proposed to provide offshore tank farms or storage facilitiesfor storing such crude oil and the like. However, offshore storage facilities are subject to several disadvantages; namely, offshore facilities are subject to wave and tide'action and relatively expensive and complicated mooring means and foundation means and strongly constructed tanks must be utilized in order to withstand the wave and tide action. Further, as the number of offshore storing facilities increase, there is an ever-increasing problem of pollution of the surrounding body of water and adjacent shore areas due to spillage or leakage of the stored crude oil.

The present invention provides a unique and simple solution to the aforementioned problems. By means of the present invention, a protected area is provided in a body of water which is subject to wave and tide action and tanks for storing the-crude oil and the like are moored in the protected area. For example, the protected area can be provided by a diked area in the body of water comprising either man-made dike walls or a combination of man-made dike wall structures and a shoreline, or in a naturally protected area.

The. present invention is concerned primarily with the provision of a diked area in a body of water including man-made dike wall structures and in which diked areathe tanks for storing the crude oil or'the like are moored or anchored.

In particular, the present invention teaches the use of a diked area in which means are provided for protecting the diked area from wave action and for preventing leakage of spilled crude oil or the like from the diked area to the surrounding body of water or adjacent shore areas.

The tanks used in the invention are floating tanks and have fixed roofs thereon. The fixed roof construction has many advantages over existing prior art storage tanks which utilize floating roofs and seals and the like. The use of a fixed roof instead of a floating roof eliminates the peripheral seals required between a floating roof and the side wall of the tank; and such peripheral seal is the source of many problems even on land based storage tanks insofar as maintenance and the like is concerned, and such problems are magnified when used in floating tanks in a body of water. Moreover, in the present invention the oil or the like stored in the tanks actually supports at least'a portion of the weight of the roof and tank, and the unit pressure acting on the surface of the stored liquid is thus greater than that resulting from a standard floating roof. This increase in unit pressure in conjunction with the elimination of the peripheral seal results in a virtually complete prevention of any out-gassing evaporation of the light ends of the stored oil or other liquid. This results in a substantial savings over the life'of the tank and prevents the possibility of any hydrocarbons or aromatic pollutants entering the atmosphere. Further, the design and use of roof drains for a fixed roof tank is much simpler and safer than those for a floating roof; and, in fact, the drains may be eliminated altogether with a fixed roof tank. Additionally, since there is no relative movement between the fixed roof and the side walls of the invention, therewill not be an oil wetting/drying cycle for the side walls as is the case when a floating roof is used. This further prevents loss of the lighter components of the oil into the atmosphere. Still further, the fixed roof of the present invention provides a better structural base for the loading/offloading lines used in conjunction with the tank than a moving;v floating roof provides; and the fixed roof requires significantly less maintenance than a floating roof with a peripheral seal.

OBJECTS OF THE INVENTION It is an object of this invention to provide a protected offshore storage facility-for storing liquids having a density less than the density of water and'wherein the protected facility protects stsorage tanks in the facility from the action of waves and the like in the body of water and also prevents pollution of the surrounding body of water and adjacent shore areas by spilled or leaked liquid from the tanks.

Another object of the invention is to provide a dike wall structure defining a diked area protected from wave action and at least one floating tank containing a liquid of less specific gravity than water moored in the diked area and having a fixed roof thereon, the dike wall structure preventing leakage of stored product from the diked area to the surrounding body of water or adjacent shore areas.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top perspective view of a protected storage facility in accordance with the invention;

FIG. 2 is a view in section taken along line 2--2 in FIG. 1;

FIG. 3 is a view in section taken along line 3-3 in FIG. 1;

FIG. 4 is a section taken along line 4-4 in FIG. 1;

FIG. 5 is a view in section taken along line 5-5 in FIG. 1;

FIG. 6 is a view in section taken along line 6-6 in FIG. 1;

FIG. 7 is a greatly enlarged view with portions broken away showing one of the storage tanks of the invention in cross section;

invention showing a still further form of buoyancy means therefor; and,

FIGS. 12 through are fragmentary sectional views of a tank in accordance with the invention in different operative conditions thereof and showing the relationship between the tank, the surrounding body of water and liquid stored in the tank.

DETAILED DESCRIPTION OF THE INVENTION In the drawings, like reference numerals indicate like parts throughout the several views, and a protected offshore storage facility in accordance with the invention is indicated generally at- 10. The protected storage facility includes a man-made dike wall structure 11 including a pair of spaced apart generally parallel dike walls 12 and 13 extending substantially perpendicularly from a shoreline S into a body of water W and a dike wall I4 extending between and connected to the ends of the walls 12 and 13 in the body of water to enclose and define a protected body of water 15 which is not subject to wave action and the like in the surrounding body of water W.

The body of water 15 comprises a main pool or storage pool in which a plurality of tanks T are moored by suitable mooring lines indicated in phantom lines L. A plurality of pipes or conduits or the like P extend through the dike wall 14 near the bottom thereof for conveying water from the surrounding body of water W into the protected pool 15. The number and size of the pipes P is such that inflowing water does not create turbulence in the pool 15; and as seen in FIG. 3, a one-way valve means V is on the end of the pipes P within the body of water 15 for preventing flow of water from the pool back through the pipes to the surrounding body of water W. Thus, as the tide rises in the surrounding body of water W, the water will flow inwardly through the pipes P and the valves V to the protected area or pool 15, and the tanks T accordingly rise and fall with the rise and fall of tide in the surrounding body of water and in the pool 15.

A liquid impervious shield or barrier B is secured to each dike wall l2, l3 and 14 at the upper inner side thereof in the pool 15 and the barriers B extend from the top of the walls to below the water line in the pool to prevent any stored liquid which may have leaked or spilled from the tanks and which is floating on the water in the pool 15 from seeping through the dike walls into the surrounding body of water.

A pair of spaced apart, substantially parallel dike walls 16 and 17 are each connected at one end thereof with the dike wall 13 adjacent the opposite ends of the dike wall 13 and extend perpendicularly from the wall 13 into the surrounding body of water.

Another dike wall 18 extends between and is connected to the dike walls 16 and 17, and a further dike wall 19 is connected at its opposite ends to the wall 13 and the wall 18, respectively, and divides the area bounded by the walls 13, 16, 17 and 18 into an intermediate pool 20 and a final pool 21.

A pipe means P extends through the wall 13 adjacent the bottom thereof from the pool 15 to the pool 20 for flow of water from the pool 15 to the intermediate pool; and as seen in FIG. 4, a suitable one-way valve means V is on the end pipe P in intermediate pool 20 for enabling fiow from the main pool 15 to intermediate pool 20 but preventing reverse flow therethrough.

As seen in FIG. 5, the dike wall or partition 19 comprises a graded rock filter F and has a barrier means B on each of the opposite sides thereof at its upper end and the graded rock filter F enables flow of water from the intermediate pool 20 to the final pool 21 but separates any spilled oil or the like from the water so that only clean water flows into the pool 21. The barriers B at the top of the dike wall 19 further insure that only clean water flows from pool 20 to pool 21.

From the final pool 21, the water is caused to flow through an oil field type oil/water separator 22 mounted on top of the dike wall 17 back into the body of water W, the oil/water separator 22 insuring that positively no spilled or leaked liquid from the tanks is permitted to flow into the surrounding body of water With the above described structure, as the tide rises in a surrounding body of water W, water flows inwardly through the pipes P to the main pool 15', and when the tide falls in the surrounding body of water, the water in the pool 15 flows through the pipes P into the intermediate pool 20 and from the intermediate pool 20 through the graded rock filter F into the final pool 21 and from the final pool 21 through the oil/water separator 22 back into the surrounding body of water W. The pipes P and P prevent any reverse flow of water from the pools to the surrounding body of water, and the graded rock filter F, oil/water separator 22 and barriers B prevent seepage or leakage of spilled stored product from the pools into the surrounding body of water, thus completely avoiding any pollution of the surrounding body of water or adjacent shore areas.

The dike walls in a preferred construction are made of concrete or like material although the dike walls may be made of any other suitable material, and it is not essential that the dike walls and diked area assume the particular configuration as shown and described. Further, one tank or any number of tanks greater than one could be moored in the main pool or storage pool 15 as desired.

Various constructions of the storage tanks are illustrated in FIGS. 7 through 11, and in FIG. 7 a tank T is shown floating in the pool 15 and is filled with oil, the oil/water interface being spaced upwardly from the open bottom 23 of the tank. An annular T-section girder 24 is suitably secured as by welding or the like to the inner marginal surface of the open bottom of the tank, and a plurality of gussets 25 are secured to the ring shaped girder 24 at spaced intervals therearound, and the mooring lines L are secured at one end to the gussets 25 and at their other ends to suitable fixed rlnsooring means or anchors A in the bottom of the pool The fixed roof R is secured to the top of the tank T and extends radially outwardly at its outer marginal edge 26 beyond the top of the side wall of the tank. A plurality of T-section stiffeners 27 are suitably secured as by welding or the like to the top surface of roof R for stiffening and reinforcing the roof.

An annular, hollow, ring-shaped buoyancy means or compartment 28 is suitably affixed to the upper outer surface of the side wall of the tank and comprises an annular, cylindrical, vertically extending wall 29 secured as by welding or the like at its upper edge to the outer edge of the marginal portion 26 of the roof R and secured as by welding or the like at its lower edge to an annular, horizontal, ring-shaped bottom wall 30 which is welded or otherwise secured between the bottom edge of thewall 29 and the side wall of the tank T.

In FIGS. 8 and 9, a slightly modified buoyancy means 28' is illustrated and is substantially identical to the buoyancy means 28 of FIG. 7 except that a plurality of vertically extending, circumferentially spaced T- section stiffeners 31 and 32 are welded or otherwise suitably secured to the wall 29 of the buoyancy ring and the outer surface of the side wall of the tank, respectively. A plurality of reinforcing bars 33 are then welded between the stiffening members 31 and 32 in a zig-zag relationship.

In FIG. 10, a further modified buoyancy means 28" is illustrated and is substantially the same as that illustrated in FIG. 7 except that the hollow buoyancy ring is filled with a suitable buoyant material such as foam or the like 34.

In FIG. II, a still further modified construction is illustrated and in addition to the foam filled buoyancy ring 28" on the outer upper surface of the side wall of the tank T, a pair of concentric, radially spaced buoyancy rings 35 and 36 are suitably secured to the underside of the roof R concentrically with the axis of the tank T. More than one buoyancy ring or only one buoyancy ring may be provided, as desired, or the buoyancy rings 35 and 36 may be omitted entirely, and the buoyancy rings may comprise a foam material or any other suitable buoyant material as desired.

The tanks may be provided with fixed, closed bottoms (not shown) if desired, and as seen in FIG. 1 in operative association with some of the tanks, suitable conduit means C are connected with the tanks for loading and unloading the tanks.

By way of specific example, a tank T in accordance with the invention has a diameter of from about 100 feet to about 250 feet and is about 60 feet high and has a storage capacity of about 300,000 barrels of oil or other liquid.

In FIGS. 12 through 15, various operational conditions of the tank are illustrated.

In FIG. 12, an empty tank T is shown floating at the surface of a body of water in the pool 15, and the buoyancy ring 28 is sufficient to maintain the tank floating at approximately the level illustrated with a pocket of air beneath the roof R of the tank above the surface of the water therein.

In FIG. I3, oil is being pumped into the tank, and a layer of oil is shown on the surface of the water.

In FIG. 14, the tank T is illustrated full of oil and as the oil is pumped into the tank, it displaces the water therefrom through the open bottom of the tank. Since the density of the water is greater than that of the oil, the oil will actually rise above the surface of the water and will exert a pressure on the underside of the roof R and will impart buoyancy to the tank in addition to the buoyancy imparted thereto from the buoyancy ring As discussed previously, the unit pressure exerted on the oil by the weight of the tank and the roof supported thereon reduces the tendency of the oil to evaporate and prevents the formation of a vapor pocket or space in the tank regardless of whether the tank is full or empty since as seen in FIG. 15, even when substantially all of the oil is pumped from the tank, a heel or a layer 37 of oil remains in the tank and fills the space between the inner surface of the roof R and the surface of the water.

Accordingly, with the above described structure, a simple and unique storage facility is provided wherein at least one storage tank for storing a liquid of less density than that of water is moored in a protected body of water such that the tank is protected from the wave action of the surrounding body of water, and any stored product which spills or leaks from the tanks is confined to the protected area and thus pollution of the surrounding body of water or an adjacent shore area is prevented. Moreover, the particular construction of the tanks wherein they are floated in the body of water and have fixed roofs thereon overcomes several disadvantages which exist in prior art tanks; namely, the necessity of a peripheral seal as required with a floating roof is obviated, and the pressure exerted on the surface of the oil by the weight of the tank and roof completely prevents any evaporation or outgassing of the light ends of the stored oil, and maintenance for the fixed roof tank is substantially less than that of conventional floating roof tanks.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore il lustrated and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are, therefore, intended to be enbraced by those claims.

What is claimed is:

1. In combination: a rigid dike wall structure having opposite, spaced apart end walls extending from a shore of a body of water subject to wave and tide action and into the body of water, and a front wall connected to the end walls and extending in the body of water in spaced relation to the shore of the body of water, said dike wall structure extending from the floor of the body of water to above the surface of the body of water and enclosing a body of water protected from the wave action of the surrounding body of water; first flow control means in said dike wall structure to enable flow from the surrounding body of water into the enclosed body of water; a plurality of floating tanks moored side-byside in the enclosed, protected body of water to store a liquid product having a specific gravity less than the specific gravity of the body of water, said tanks having a side wall with an open bottom and a fixed roof and buoyancy means connected with each tank to float the tank at the surface of the protected body of water; conduit means connected with the tanks to add product to and remove product from the tanks; and second flow control means in said dike wall structure to enable flow of water from the enclosed body of water to the surrounding body of water, but to prevent flow of leaked or spilled product from the enclosed body of water to said surrounding body of water, said dike wall structure thus protecting the tanks in the enclosed body of water from the wave and tide action of the surrounding body 7 of water and also preventing contamination of the surrounding body of water by any product leaked or spilled from the tanks.

2. The combination of claim I, wherein at least one annular buoyancy ring is secured to the underside of the fixed roof.

3. The combination of claim 2, wherein said annular buoyancy ring secured to said side wall is filled with a buoyant foam material.

4. The combination of claim 1, wherein said end walls comprise a pair of substantially parallel, elongate dike walls connected at one of their ends to said shore and extending at their other ends into said body of wa' ter, and said front wall extends substantially parallel to said shore and is joined at its opposite ends to the other ends of said end walls to enclose said body of water and define said diked area.

5. The combination of claim 1, wherein said second flow control means includes additional dike walls connected with one of said end walls extending from said shore, and in cooperation with said one end wall enclose an additional body'of water adjacent said diked area, means in said end wall establishing fluid flow communication between the diked area and the additional body of water, means associated with said fluid flow communicating means to enable flow from the diked area into said additional body of water but preventing reverse flow, and means in said additional dike wall structure establishing fluid flow communication from said additional body of water to the surrounding body of water.

6. The combination of claim 5, wherein liquid impervious means is attached to said dike wall structure to prevent leakage or seepage of stored product from the diked area into the surrounding body of water.

7. The combination of claim 6, wherein a graded rock filter extends across said additional body of water and separates the additional body of water into an intermediate pool and a final pool, and flow control means are connected with said dike walls to only enable flow to occur from the surrounding body of water into the diked area, from the diked area to the intermediate pool, from the intermediate pool through the graded rock filter and into the final pool, and from the final pool back into the surrounding body of water.

8. The combination of claim 7, wherein an oil/water separator is connected between the final pool and the surrounding body of water for flow of water from the final pool to the surrounding body of water.

9. The combination of claim 8, wherein a plurality of T-sections stiffener means are secured to said fixed roof for reinforcing and stiffening said roof.

10. The combination of claim 9, wherein a plurality of zig-zag reinforcing bars are secured inside said annular buoyancy ring to reinforce the buoyancy ring. 

1. In combination: a rigid dike wall structure having opposite, spaced apart end walls extending from a shore of a body of water subject to wave and tide action and into the body of water, and a front wall Connected to the end walls and extending in the body of water in spaced relation to the shore of the body of water, said dike wall structure extending from the floor of the body of water to above the surface of the body of water and enclosing a body of water protected from the wave action of the surrounding body of water; first flow control means in said dike wall structure to enable flow from the surrounding body of water into the enclosed body of water; a plurality of floating tanks moored side-by-side in the enclosed, protected body of water to store a liquid product having a specific gravity less than the specific gravity of the body of water, said tanks having a side wall with an open bottom and a fixed roof and buoyancy means connected with each tank to float the tank at the surface of the protected body of water; conduit means connected with the tanks to add product to and remove product from the tanks; and second flow control means in said dike wall structure to enable flow of water from the enclosed body of water to the surrounding body of water, but to prevent flow of leaked or spilled product from the enclosed body of water to said surrounding body of water, said dike wall structure thus protecting the tanks in the enclosed body of water from the wave and tide action of the surrounding body of water and also preventing contamination of the surrounding body of water by any product leaked or spilled from the tanks.
 2. The combination of claim 1, wherein at least one annular buoyancy ring is secured to the underside of the fixed roof.
 3. The combination of claim 2, wherein said annular buoyancy ring secured to said side wall is filled with a buoyant foam material.
 4. The combination of claim 1, wherein said end walls comprise a pair of substantially parallel, elongate dike walls connected at one of their ends to said shore and extending at their other ends into said body of water, and said front wall extends substantially parallel to said shore and is joined at its opposite ends to the other ends of said end walls to enclose said body of water and define said diked area.
 5. The combination of claim 1, wherein said second flow control means includes additional dike walls connected with one of said end walls extending from said shore, and in cooperation with said one end wall enclose an additional body of water adjacent said diked area, means in said end wall establishing fluid flow communication between the diked area and the additional body of water, means associated with said fluid flow communicating means to enable flow from the diked area into said additional body of water but preventing reverse flow, and means in said additional dike wall structure establishing fluid flow communication from said additional body of water to the surrounding body of water.
 6. The combination of claim 5, wherein liquid impervious means is attached to said dike wall structure to prevent leakage or seepage of stored product from the diked area into the surrounding body of water.
 7. The combination of claim 6, wherein a graded rock filter extends across said additional body of water and separates the additional body of water into an intermediate pool and a final pool, and flow control means are connected with said dike walls to only enable flow to occur from the surrounding body of water into the diked area, from the diked area to the intermediate pool, from the intermediate pool through the graded rock filter and into the final pool, and from the final pool back into the surrounding body of water.
 8. The combination of claim 7, wherein an oil/water separator is connected between the final pool and the surrounding body of water for flow of water from the final pool to the surrounding body of water.
 9. The combination of claim 8, wherein a plurality of T-sections stiffener means are secured to said fixed roof for reinforcing and stiffening said roof.
 10. The combination of claim 9, wherein a plurality of zig-zag reinforcing bars are secured inside said annulaR buoyancy ring to reinforce the buoyancy ring. 